1. Field of the Invention
This invention relates to cutting threads into short sections, particularly threads in the form of rovings of untwisted or slightly twisted strands of a mineral substance such as glass fibers.
Short pieces of glass fiber rovings, usually in lengths between three to six millimeters have been found to be useful as a reinforcement material in synthetic polymeric resins which are cast or molded into complex shapes. Rovings possess relatively little cohesion, and as a consequence, the individual strands of which they are constituted tend to separate during the cutting operation in which the pieces are cut from a continuous length of roving. This results in the formation of a considerable quantity of waste material in the form of fibers and particles which, as the cutting operation proceeds, tends to fill and to be packed into the spaces between cutting blades carried by a rotating cutting drum, and this tends to make the cutting process faulty.
2. Description of the Prior Art
It has been known to cut rovings into short lengths by the use of a rotating drum having radially extending cutting blades, which drum acts in conjunction with a rotating support drum; the rovings being carried on the support drum and being cut by the blades as the blades come into contact with the surface of the support drum.
U.S. Pat. No. 3,555,947 shows such roving cutting apparatus employing means for ejecting the cut pieces from between adjacent cutting blades. In that device, a drum formed of a plurality of ejecting bars is mounted for rotation eccentrically with respect to the axis of rotation of the drum to which the cutting blades are attached. Ejection of the cuttings is confined to a very narrow area immediately adjacent the point of cutting. Further, this device has no means for preventing the waste material resulting from the cutting action from accumulating in the spaces between the blades. The buildup of waste material between the blades can be quite considerable, particularly where short lengths are being cut, and it is difficult to remove because of the formation of electrostatic fields which tend to cause the waste material to be retained in the spaces between the cutting blades.